57 A multiple-disc filter comprises a stack of filtering discs (114) each formed with grooves extending only partially through the thickness of the disc (114) and configured to define a continuous, non-apertured surface on one face and a plurality of spaced ribs (140) projecting from the opposite faces. The ribs are connected together to define a sinuous configuration and have straight line edges. The stack further includes spacing ribs (151,152,153) between the confronting faces of adjacent discs of the stack for spacing the straight line edges of the sinuous ribs (140) of one disc (114) from the confronting face of the next adjacent disc (114) in the stack, such that the confronting faces of adjacent discs (114) define a first group of recesses (161) between the ribs (140) communicating with a filter inlet (104), a second group of recesses (162) alternating with the first group of recesses (161) and communicating with a filter outlet (106), and a plurality of filtering passageways (163) between the straight line edges of the ribs (140) and the confronting face of the next adjacent disc (114).